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Conjugated linoleic acid (CLA)

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Also listed as: CLA
Related terms
Background
Evidencetable
Tradition
Dosing
Safety
Interactions
Attribution
Bibliography

Related Terms
  • ALLMAX Nutrition® CLA95, catalpic acid, CFA-S, CLA by-product, CLA triglyceride oil, CLA-60, CLA-FFA, CLA-free fatty acid (FFA), ClarinolT, ClarinolT A-65, ClarinolT A-80, ClarinolT A-95, ClarinolT G-80, CLA-triacylglycerol, CLN, CLnA, CLNA, conjugated alpha-linolenic acid (CLnA), conjugated diene isomers of linoleic acid, conjugated dienoic derivatives of linoleic acid, conjugated dienoic isomers of linoleic acid, conjugated fatty acids, conjugated linolenic acid, conjugated octadecatrienoic (CLnA) acids, dietary CLA, dietary conjugated linoleic acid, LA, linoleic acid, linolelaidic acid, lipid esterified conjugated linoleic acid, octadecadienoate (18:2), octadecadienoic acids, polyunsaturated fatty acids, positional and geometric isomers of a conjugated diene of linoleic acid, pure conjugated linoleic acid, RA, rumenic acid, ruminant meat, SafflorinT, SafflorinT isomerized safflower oil, safflower oil, sunflower oil, synthetic conjugated linoleic acid mixture, t10c12-CLA, t10,c12-CLA, Tonalin®, Tonalin® CLA, VA, vaccenic acid.
  • Combination product examples: ProMassT (gamma-linolenic acid and CLA).

Background
  • Conjugated linoleic acid (CLA) is a fatty acid that is naturally found in beef and dairy products. CLA levels in dairy products may be modified by changing the animals' diets. Most CLA dietary supplements are made from safflower oil. However, CLA is also found in other vegetable oils, including hydrogenated soybean oil.
  • Scientific interest in CLA began in the 1980s as a result of early evidence suggesting anticancer effects. Since this time, interest in CLA has broadened to areas of weight loss, exercise performance enhancement, and altered body composition. Conjugated linoleic acid is now a wide-selling supplement marketed to reduce obesity and body fat. Conjugated linoleic acid has also been studied for its effects on allergy, asthma, hair loss, heart disease risk, diabetes, high cholesterol, high blood pressure, immune function, and rheumatoid arthritis. The two dominant isomers, or forms, of CLA that have been studied are the cis-9,trans-11 (c9,t11) and the trans-10,cis-12 (t10,c12) forms.

Evidence Table

These uses have been tested in humans or animals. Safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider. GRADE *


Conjugated linoleic acid (CLA) is a popular supplement marketed to reduce obesity and body fat. While some human evidence suggests that CLA may reduce body fat mass and body weight, results of other studies failed to show these effects. Additional research is needed in this area before firm conclusions can be made.

B


Limited research suggests that CLA may reduce sneezing due to birch pollen allergy. Further research is needed.

C


Limited human research showed that CLA may help asthma patients' lung function. Additional research is needed in this area.

C


Although early evidence suggested that CLA had anticancer effects, human studies are needed to investigate the potential anticancer potential of CLA.

C


Some, but not all, human studies showed a decrease in blood pressure with CLA treatment. Additional research is needed to investigate the possible cardiovascular effects of CLA.

C


Early evidence suggested that CLA might increase insulin sensitivity and reduce blood glucose; however, other studies have suggested that CLA increases insulin resistance in humans. Additional research is needed in this area before a conclusion can be made.

C


Results from studies of the effects of CLA on exercise performance are mixed. Additional research is needed in this area before a conclusion can be made.

C


Preliminary research showed reduced hair loss after CLA treatment. More research is needed in this area.

C


Early evidence suggests that CLA supplementation may reduce or prevent high blood pressure. Additional research is needed in this area before a conclusion can be made.

C


Early evidence suggests that CLA supplementation may have beneficial effects on blood lipids. Additional research is needed in this area before a conclusion can be made.

C


Based on human research, CLA may have small, significant effects on some immune markers. Additional research is needed in this area before a conclusion can be made.

C


Limited research showed that CLA decreased pain, stiffness, and medication needs in patients with rheumatoid arthritis. Additional research is needed.

C
* Key to grades

A: Strong scientific evidence for this use
B: Good scientific evidence for this use
C: Unclear scientific evidence for this use
D: Fair scientific evidence for this use (it may not work)
F: Strong scientific evidence against this use (it likley does not work)


Tradition / Theory

The below uses are based on tradition, scientific theories, or limited research. They often have not been thoroughly tested in humans, and safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider. There may be other proposed uses that are not listed below.

  • Aging, allergies, antibacterial, antioxidant, anorexia (eating disorder), arthritis, atopic dermatitis (eczema), bone loss, cachexia (weight loss/wasting from some diseases), colitis (intestinal inflammation), common cold, depression, fertility, food uses, growth, infection, human papillomavirus (HPV), inflammation, inflammatory bowel disease, influenza, liver protection, metabolic syndrome, muscular dystrophy, nerve disorders, obesity/weight loss, skin conditions, sore throat, systemic lupus erythematosus (autoimmune disorder), wound healing.

Dosing

Adults (18 years and older)

  • In humans, the estimated daily intake of CLA is 0.35 grams daily for women and 0.43 grams daily for men, predominantly from milk, milk products, and some meats.
  • There is no proven safe or effective dose for CLA.
  • For allergy, two grams of CLA has been taken by mouth daily for 12 weeks.
  • For asthma, 4.5 grams of CLA has been taken by mouth daily for 12 weeks.
  • For cardiovascular (heart) disease risk factors, up to four grams of CLA has been taken by mouth daily for up to six months.
  • For diabetes, doses of CLA of up to 6.4 grams have been taken by mouth daily for up to 16 weeks.
  • For exercise performance enhancement, doses ranging from 3.9 to 6 grams of CLA have been taken by mouth for 28 days to 12 weeks.
  • For high cholesterol, 3-3.9 grams of CLA has been taken by mouth daily for 56-63 days. One liter of milk daily naturally enriched with 4.2% of the cis-9,trans-11 (c9,t11) form of CLA has been taken by mouth for eight weeks.
  • For high blood pressure, 4.7 grams of CLA has been taken by mouth daily for five weeks.
  • For immune function, 1.7 grams of ClarinolT or 1.6 grams of mixed CLA isomers has been taken by mouth daily for 12 weeks. Two to 3.9 grams of CLA has been taken daily for up to 63 days. Two grams of mixed CLA isomers has been taken by mouth daily for four weeks.
  • For obesity/weight loss, body fat mass, abdominal diameter, or body weight reduction, up to 6.8 grams of CLA has been taken by mouth for as long as two years. For weight maintenance after weight loss, up to 3.6 grams of CLA has been taken by mouth daily for up to one year. Clinical trials have used up to 4.5 grams of CLA taken by mouth daily for up to 12 weeks or 2.59 grams of CLA in butter taken by mouth for four weeks. Also, 3.4 grams of a purified trans-10,cis-12 (t10,c12) isomer of CLA has been taken by mouth daily for 12 weeks; 1.5 or 3 grams of c9,t11 CLA, 1.5 grams or 3 grams of t10,c12 CLA have been taken by mouth; 80% c9,t11 CLA isomer-enriched (0.59, 1.19, and 2.38 grams daily) or 80% t10,c12 CLA (0.63, 1.26, and 2.52 grams daily) has been taken by mouth for 24 weeks; 500 milliliters of fortified milk containing three grams of CLA has been taken by mouth daily for four months; and 3.2 grams of CLA has been taken by mouth daily (equal amounts of c9,t11 and t10,c12 isomers) for 12 weeks. Milk containing three grams of ClarinolT Lipid Nutrition per serving has been taken by mouth daily for an average of seven months. Three grams of CLA in 500 milliliters of skim milk has been taken by mouth daily for 12 weeks, and 3.76 grams of triacylglycerols (Tonalin 75 TG®) with equal amounts of the c9,t10 and t10,c12 isomers in yogurt has been taken by mouth daily for 14 weeks. One liter of milk naturally enriched with 4.2% of c9,t11 isomer alone has been taken by mouth daily for eight weeks; 0.7 grams of CLA has been taken by mouth daily for four weeks, followed by 1.4 grams of CLA taken by mouth daily for four weeks. CLA (3.4 grams) has been taken by mouth daily for 12 weeks; 2.1 grams of mixed CLA has been taken by mouth for 45 days. According to secondary sources, 2-3 grams of CLA with breakfast, lunch, and dinner was suggested.
  • For rheumatoid arthritis, five grams of mixed CLA isomers has been taken by mouth daily for 12 weeks.

Children (under 18 years old)

  • There is no proven safe or effective dose for CLA in children.

Safety

The U.S. Food and Drug Administration does not strictly regulate herbs and supplements. There is no guarantee of strength, purity or safety of products, and effects may vary. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare provider before starting a new therapy. Consult a healthcare provider immediately if you experience side effects.

Allergies

  • Insufficient evidence is available on allergy or sensitivity to conjugated linoleic acid (CLA).

Side Effects and Warnings

  • Conjugated linoleic acid (CLA) is generally well tolerated in healthy adults at doses up to 3.4 grams for as long as two years, or 6.4 grams for 12-16 weeks.
  • Caution is advised in patients with diabetes or hypoglycemia, those at risk of diabetes, and those taking drugs, herbs, or supplements that affect blood sugar. Blood glucose levels may need to be monitored by a qualified healthcare professional, including a pharmacist. Medication adjustments may be necessary. Increases in insulin resistance and glucose concentrations and decreases in insulin sensitivity and blood leptin (energy hormone) levels have been reported with CLA use.
  • CLA may affect blood cholesterol levels. Caution is advised when using medications that may also affect cholesterol.
  • CLA may increase the risk of bleeding. Caution is advised in patients with bleeding disorders or in those taking agents that may increase the risk of bleeding. Dosing adjustments may be necessary.
  • CLA may cause low blood pressure. Caution is advised in patients taking drugs, herbs, or supplements that lower blood pressure.
  • CLA may cause abdominal distension, bloating, diarrhea, esophageal irritation, gas, heartburn, nausea, rash, hives, autoimmune symptoms, backache, headache, unpleasant personal odor, or weight gain. CLA may affect liver function.
  • Use cautiously in patients with gastrointestinal disorders, heart disease, immune disorders, or skin disorders, and in those at risk for inflammatory disorders.
  • Use cautiously in children and pregnant or breastfeeding women.
  • Avoid in patients with liver disorders.

Pregnancy and Breastfeeding

  • Use cautiously in children and pregnant or breastfeeding women, as safety has not been systematically studied in these populations.

Interactions

Interactions with Drugs

  • Conjugated linoleic acid (CLA) may increase the risk of bleeding when taken with drugs that increase the risk of bleeding. Some examples include aspirin, anticoagulants (blood thinners) such as warfarin (Coumadin®) or heparin, antiplatelet drugs such as clopidogrel (Plavix®), and nonsteroidal anti-inflammatory drugs (NSAIDS) such as ibuprofen (Motrin®, Advil®) or naproxen (Naprosyn®, Aleve®).
  • CLA may lower blood pressure. Caution is advised when using medications that may also lower blood pressure.
  • CLA may affect blood cholesterol levels. Caution is advised when using medications that may also affect cholesterol.
  • CLA may affect blood sugar levels. Caution is advised when using medications that may also affect blood sugar. Patients taking insulin or drugs for diabetes by mouth should be monitored closely by their qualified healthcare professionals, including pharmacists. Medication adjustments may be necessary.
  • CLA may also interact with antibiotics, antibodies, antidepressants, anticancer drugs, anti-inflammatory drugs, antiobesity drugs, calcium salts, cardiovascular drugs, corticosteroids, drugs for skin conditions, drugs that affect the immune system, drugs that may damage the liver, exercise performance enhancers, fertility agents, gastrointestinal drugs, hematologic agents, hormonal agents, neurologic drugs, osteoporosis drugs, polyethylene glycol (PEG), and surfactants (surface-active agents).

Interactions with Herbs and Dietary Supplements

  • Conjugated linoleic acid (CLA) may increase the risk of bleeding when taken with herbs that increase the risk of bleeding. Multiple cases of bleeding have been reported with the use of Ginkgo biloba, and fewer cases with garlic and saw palmetto. Numerous other agents may theoretically increase the risk of bleeding, although this has not been proven in most cases.
  • CLA may lower blood pressure. Caution is advised when using herbs or supplements that may also lower blood pressure.
  • CLA may affect blood cholesterol levels. Caution is advised when using herbs or supplements that may also affect cholesterol.
  • CLA may affect blood sugar levels. Caution is advised when using herbs or supplements that may also affect blood sugar levels.
  • CLA may also interact with agents that may damage the liver, ajoene, alpha-lipoic acid, alpha-tocopherol, antibacterials, antidepressants, anticancer herbs, anti-inflammatory herbs or supplements, antiobesity herbs or supplements, antioxidants, arginine, athletic performance enhancers, beta-cyclodextrin, betaine, beta-lactoglobulin, beta-sitosterol, black currant seed, calcium, cardiovascular herbs and supplements, chromium picolinate, cobalt, coconut oil, conjugated linolenic acid (CLNA), creatine, fatty acids, fertility agents, gastrointestinal herbs or supplements, glutamine, herbs or supplements for skin conditions, herbs or supplements that affect the immune system, hormonal herbs and supplements, L-carnitine, neurologic herbs or supplements, oleic acid, omega-3 fatty acids, osteoporosis herbs or supplements, probiotics, propionic acid, resveratrol, selenized yeast, sesamin, soy, vaccenic acid, vitamin A, and sitosterol, as well as with antioxidant-rich diets, beef, butter, calcium-rich diets, cheese, coconut oil, eggs, an essential fatty acid-deficient diet, fiber, flaxseed oil, lipid-lowering diets, low-protein diets, milk, omega-3 fatty acids, and pine nut oil.

Attribution
  • This information is based on a systematic review of scientific literature edited and peer-reviewed by contributors to the Natural Standard Research Collaboration (www.naturalstandard.com).

Bibliography
  1. Brownbill RA, Petrosian M, and Ilich JZ. Association between dietary conjugated linoleic acid and bone mineral density in postmenopausal women. J Am Coll Nutr 2005;24(3):177-181.
  2. Eyjolfson V, Spriet LL, and Dyck DJ. Conjugated linoleic acid improves insulin sensitivity in young, sedentary humans. Med Sci Sports Exerc 2004;36(5):814-820.
  3. Gaullier JM, Halse J, Hoye K, et al. Supplementation with conjugated linoleic acid for 24 months is well tolerated by and reduces body fat mass in healthy, overweight humans. J Nutr 2005;135(4):778-784.
  4. Herrera JA, Arevalo-Herrera M, Shahabuddin AK, et al. Calcium and conjugated linoleic acid reduces pregnancy-induced hypertension and decreases intracellular calcium in lymphocytes. Am J Hypertens 2006;19(4):381-387.
  5. MacRedmond R, Singhera G, Attridge S, et al. Conjugated linoleic acid improves airway hyper-reactivity in overweight mild asthmatics. Clin Exp Allergy 2010;40(7):1071-1078.
  6. Michishita T, Kobayashi S, Katsuya T, et al. Evaluation of the antiobesity effects of an amino acid mixture and conjugated linoleic acid on exercising healthy overweight humans: a randomized, double-blind, placebo-controlled trial. J Int Med Res 2010;38(3):844-859.
  7. Moloney F, Yeow TP, Mullen A, et al. Conjugated linoleic acid supplementation, insulin sensitivity, and lipoprotein metabolism in patients with type 2 diabetes mellitus. Am J Clin Nutr 2004;80(4):887-895.
  8. Nugent AP, Roche HM, Noone EJ, et al. The effects of conjugated linoleic acid supplementation on immune function in healthy volunteers. Eur J Clin Nutr 2005;59(6):742-750.
  9. Pinkoski C, Chilibeck PD, Candow DG, et al. The effects of conjugated linoleic acid supplementation during resistance training. Med Sci Sports Exerc 2006;38(2):339-348.
  10. Racine NM, Watras AC, Carrel AL, et al. Effect of conjugated linoleic acid on body fat accretion in overweight or obese children. Am J Clin Nutr 2010;91(5):1157-1164.
  11. Rastmanesh, R. An urgent need to include risk-benefit analysis in clinical trials investigating conjugated linoleic acid supplements in cancer patients. Contemp Clin Trials 9-21-2010.
  12. Riserus U, Arner P, Brismar K, et al. Treatment with dietary trans10cis12 conjugated linoleic acid causes isomer-specific insulin resistance in obese men with the metabolic syndrome. Diabetes Care 2002;25(9):1516-1521.
  13. Sluijs I, Plantinga Y, de Roos B, et al. Dietary supplementation with cis-9,trans-11 conjugated linoleic acid and aortic stiffness in overweight and obese adults. Am.J Clin.Nutr 2010;91(1):175-183.
  14. Venkatramanan S, Joseph SV, Chouinard PY, et al. Milk enriched with conjugated linoleic acid fails to alter blood lipids or body composition in moderately overweight, borderline hyperlipidemic individuals. J Am Coll Nutr 2010;29(2):152-159.
  15. Wanders AJ, Brouwer IA, Siebelink E, et al. Effect of a high intake of conjugated linoleic acid on lipoprotein levels in healthy human subjects. PLoS One 2010;5(2):e9000.

Copyright © 2011 Natural Standard (www.naturalstandard.com)


The information in this monograph is intended for informational purposes only, and is meant to help users better understand health concerns. Information is based on review of scientific research data, historical practice patterns, and clinical experience. This information should not be interpreted as specific medical advice. Users should consult with a qualified healthcare provider for specific questions regarding therapies, diagnosis and/or health conditions, prior to making therapeutic decisions.

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